// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// https://developers.google.com/protocol-buffers/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

package com.google.protobuf;

import java.io.IOException;

/**
 * This class is used internally by the Protocol Buffer library and generated message
 * implementations. It is public only because those generated messages do not reside in the {@code
 * protobuf} package. Others should not use this class directly.
 *
 * <p>This class contains constants and helper functions useful for dealing with the Protocol Buffer
 * wire format.
 *
 * @author kenton@google.com Kenton Varda
 */
public final class WireFormat {
    // Do not allow instantiation.
    private WireFormat() {
    }

    static final int FIXED32_SIZE = 4;
    static final int FIXED64_SIZE = 8;
    static final int MAX_VARINT32_SIZE = 5;
    static final int MAX_VARINT64_SIZE = 10;
    static final int MAX_VARINT_SIZE = 10;

    public static final int WIRETYPE_VARINT = 0;
    public static final int WIRETYPE_FIXED64 = 1;
    public static final int WIRETYPE_LENGTH_DELIMITED = 2;
    public static final int WIRETYPE_START_GROUP = 3;
    public static final int WIRETYPE_END_GROUP = 4;
    public static final int WIRETYPE_FIXED32 = 5;

    static final int TAG_TYPE_BITS = 3;
    static final int TAG_TYPE_MASK = (1 << TAG_TYPE_BITS) - 1;

    /**
     * Given a tag value, determines the wire type (the lower 3 bits).
     */
    public static int getTagWireType(final int tag) {
        return tag & TAG_TYPE_MASK;
    }

    /**
     * Given a tag value, determines the field number (the upper 29 bits).
     */
    public static int getTagFieldNumber(final int tag) {
        return tag >>> TAG_TYPE_BITS;
    }

    /**
     * Makes a tag value given a field number and wire type.
     */
    static int makeTag(final int fieldNumber, final int wireType) {
        return (fieldNumber << TAG_TYPE_BITS) | wireType;
    }

    /**
     * Lite equivalent to {@link Descriptors.FieldDescriptor.JavaType}. This is only here to support
     * the lite runtime and should not be used by users.
     */
    public enum JavaType {
        INT(0),
        LONG(0L),
        FLOAT(0F),
        DOUBLE(0D),
        BOOLEAN(false),
        STRING(""),
        BYTE_STRING(ByteString.EMPTY),
        ENUM(null),
        MESSAGE(null);

        JavaType(final Object defaultDefault) {
            this.defaultDefault = defaultDefault;
        }

        /**
         * The default default value for fields of this type, if it's a primitive type.
         */
        Object getDefaultDefault() {
            return defaultDefault;
        }

        private final Object defaultDefault;
    }

    /**
     * Lite equivalent to {@link Descriptors.FieldDescriptor.Type}. This is only here to support the
     * lite runtime and should not be used by users.
     */
    public enum FieldType {
        DOUBLE(JavaType.DOUBLE, WIRETYPE_FIXED64),
        FLOAT(JavaType.FLOAT, WIRETYPE_FIXED32),
        INT64(JavaType.LONG, WIRETYPE_VARINT),
        UINT64(JavaType.LONG, WIRETYPE_VARINT),
        INT32(JavaType.INT, WIRETYPE_VARINT),
        FIXED64(JavaType.LONG, WIRETYPE_FIXED64),
        FIXED32(JavaType.INT, WIRETYPE_FIXED32),
        BOOL(JavaType.BOOLEAN, WIRETYPE_VARINT),
        STRING(JavaType.STRING, WIRETYPE_LENGTH_DELIMITED) {
            @Override
            public boolean isPackable() {
                return false;
            }
        },
        GROUP(JavaType.MESSAGE, WIRETYPE_START_GROUP) {
            @Override
            public boolean isPackable() {
                return false;
            }
        },
        MESSAGE(JavaType.MESSAGE, WIRETYPE_LENGTH_DELIMITED) {
            @Override
            public boolean isPackable() {
                return false;
            }
        },
        BYTES(JavaType.BYTE_STRING, WIRETYPE_LENGTH_DELIMITED) {
            @Override
            public boolean isPackable() {
                return false;
            }
        },
        UINT32(JavaType.INT, WIRETYPE_VARINT),
        ENUM(JavaType.ENUM, WIRETYPE_VARINT),
        SFIXED32(JavaType.INT, WIRETYPE_FIXED32),
        SFIXED64(JavaType.LONG, WIRETYPE_FIXED64),
        SINT32(JavaType.INT, WIRETYPE_VARINT),
        SINT64(JavaType.LONG, WIRETYPE_VARINT);

        FieldType(final JavaType javaType, final int wireType) {
            this.javaType = javaType;
            this.wireType = wireType;
        }

        private final JavaType javaType;
        private final int wireType;

        public JavaType getJavaType() {
            return javaType;
        }

        public int getWireType() {
            return wireType;
        }

        public boolean isPackable() {
            return true;
        }
    }

    // Field numbers for fields in MessageSet wire format.
    static final int MESSAGE_SET_ITEM = 1;
    static final int MESSAGE_SET_TYPE_ID = 2;
    static final int MESSAGE_SET_MESSAGE = 3;

    // Tag numbers.
    static final int MESSAGE_SET_ITEM_TAG = makeTag(MESSAGE_SET_ITEM, WIRETYPE_START_GROUP);
    static final int MESSAGE_SET_ITEM_END_TAG = makeTag(MESSAGE_SET_ITEM, WIRETYPE_END_GROUP);
    static final int MESSAGE_SET_TYPE_ID_TAG = makeTag(MESSAGE_SET_TYPE_ID, WIRETYPE_VARINT);
    static final int MESSAGE_SET_MESSAGE_TAG =
            makeTag(MESSAGE_SET_MESSAGE, WIRETYPE_LENGTH_DELIMITED);

    /**
     * Validation level for handling incoming string field data which potentially contain non-UTF8
     * bytes.
     */
    enum Utf8Validation {
        /**
         * Eagerly parses to String; silently accepts invalid UTF8 bytes.
         */
        LOOSE {
            @Override
            Object readString(CodedInputStream input) throws IOException {
                return input.readString();
            }
        },
        /**
         * Eagerly parses to String; throws an IOException on invalid bytes.
         */
        STRICT {
            @Override
            Object readString(CodedInputStream input) throws IOException {
                return input.readStringRequireUtf8();
            }
        },
        /**
         * Keep data as ByteString; validation/conversion to String is lazy.
         */
        LAZY {
            @Override
            Object readString(CodedInputStream input) throws IOException {
                return input.readBytes();
            }
        };

        /**
         * Read a string field from the input with the proper UTF8 validation.
         */
        abstract Object readString(CodedInputStream input) throws IOException;
    }

    /**
     * Read a field of any primitive type for immutable messages from a CodedInputStream. Enums,
     * groups, and embedded messages are not handled by this method.
     *
     * @param input          The stream from which to read.
     * @param type           Declared type of the field.
     * @param utf8Validation Different string UTF8 validation level for handling string fields.
     * @return An object representing the field's value, of the exact type which would be returned by
     * {@link Message#getField(Descriptors.FieldDescriptor)} for this field.
     */
    static Object readPrimitiveField(
            CodedInputStream input, FieldType type, Utf8Validation utf8Validation) throws IOException {
        switch (type) {
            case DOUBLE:
                return input.readDouble();
            case FLOAT:
                return input.readFloat();
            case INT64:
                return input.readInt64();
            case UINT64:
                return input.readUInt64();
            case INT32:
                return input.readInt32();
            case FIXED64:
                return input.readFixed64();
            case FIXED32:
                return input.readFixed32();
            case BOOL:
                return input.readBool();
            case BYTES:
                return input.readBytes();
            case UINT32:
                return input.readUInt32();
            case SFIXED32:
                return input.readSFixed32();
            case SFIXED64:
                return input.readSFixed64();
            case SINT32:
                return input.readSInt32();
            case SINT64:
                return input.readSInt64();

            case STRING:
                return utf8Validation.readString(input);
            case GROUP:
                throw new IllegalArgumentException("readPrimitiveField() cannot handle nested groups.");
            case MESSAGE:
                throw new IllegalArgumentException("readPrimitiveField() cannot handle embedded messages.");
            case ENUM:
                // We don't handle enums because we don't know what to do if the
                // value is not recognized.
                throw new IllegalArgumentException("readPrimitiveField() cannot handle enums.");
        }

        throw new RuntimeException("There is no way to get here, but the compiler thinks otherwise.");
    }
}
